In Remington's Pharmaceutical Sciences, 14th Ed., p 1681, published in 1970, it is reported that pill coating has been a pharmaceutical technique for well over ten centuries. For example, Rhazes (850-932 A.D.) used a mucilage for coating pills in the ninth century, and Avicenna (980-1037 A.D.) is credited with the introduction of silver and gold pill coatings into medicine. The coating of pills with finely powdered talcum, called pearl coating, was popular at one time. Gelatin coating of pills was introduced by Garot in 1838. The first sugar-coated pills in the United States were imported from France in about 1842. The first sugar-coated pill was manufactured in the United States in 1956 by Warner, a Philadelphia pharmacist. The coating of pills with tolu was done in about 1860 and twenty-four year later Unna introduced enteric coated pills.
Various pharmaceutically indicated articles of manufacture have been coated by the drug dispensing art. For example, tablets were coated to provide a more attractive dosage form, to protect its drug content from moisture and to enhance its taste. Then too, tablets were provided with a coat for releasing a drug by enteric dissolution in the intestine of a warm-blooded animal. Recently osmotic dosage forms were coated with a semipermeable rate controlling wall for delivering a drug at a known rate per unit time.
While the above mentioned dosage forms are useful in the management of health and disease, serious disadvantages are associated with them. That is, usually organic solvents are used for applying the coating to the drug and drawbacks accompany the use of organic solvents. For example, organic solvents generally are toxic and they must be substantially driven from the dosage form to avoid a hazard to the dosage form's recipient. Another drawback is organic solvents are flammable thereby possibly providing the danger of fire to the manufacturer. Also, organic solvents present an environmental problem and they require complicated recovery systems to avoid contaminating the environment, which systems are expensive to operate. It will be appreciated by those skilled in the drug dispensing art that if a coating is provided that is substantially-free of organic solvents for coating drugs, drug granules, drug powders, and the like, such a coating would have an immediate positive value and, concomitantly, represent an advancement in the drug coating art. Likewise, it will be appreciated by those versed in the dispensing art that if a delivery device is made available comprising a coating applied from a nonorganic solvent, and which delivery device possesses the thermodynamic ability to deliver a beneficial drug at a controlled rate, such a delivery device would have a practical application in the fields of human and veterinary medicine.